"@BarackObama shifts blame for HIS red line to you, me and the world. He takes zero responsibility," went a more bitter tweet.

"They are lying like they did in fast and furious, benghazi, IRS, NSA and Obama already saying he did not say ‘red line’," said a third, invoking other causes popular among the president’s critics.

Readers asked us for a fact check on whether Obama "set a red line" and now denies it. But afull reading of the question and his answer shows he never denied using the phrase or giving it the significance it has today.

Instead, we’ll more closely examine Obama’s statements, both the one that inspired the discussion on Twitter and his earlier comments on the subject. We’ll start at square one, his oldest statement, then compare it with his most recent words and then end with comments Obama used four months ago that drew little media attention but are also significant.

A reporter asked this question: "Mr. President, could you update us on your latest thinking of where you think things are in Syria, and in particular, whether you envision using U.S. military, if simply for nothing else, the safekeeping of the chemical weapons, and if you're confident that the chemical weapons are safe?"

Obama: "... I have, at this point, not ordered military engagement in the situation. But the point that you made about chemical and biological weapons is critical. That’s an issue that doesn’t just concern Syria; it concerns our close allies in the region, including Israel. It concerns us. We cannot have a situation where chemical or biological weapons are falling into the hands of the wrong people.

We have been very clear to the Assad regime, but also to other players on the ground, that a red line for us is we start seeing a whole bunch of chemical weapons moving around or being utilized. That would change my calculus. That would change my equation. ..."

The key points: The reporter raised the issue of the U.S. using force. Obama said he had no plans at the moment but that would change if chemical weapons were used. There was no confusion. The red line described the point at which military force couldbe brought to bear.

A reporter asked: "Have you made up your mind to take action against Syria, whether or not you have a congressional resolution approved? Is a strike needed in order to preserve your credibility for when you set these sort of red lines?"

Obama: "Let me unpack the question. First of all, I didn’t set a red line; the world set a red line. The world set a red line when governments representing 98 percent of the world’s population said the use of chemical weapons are abhorrent and passed a treaty forbidding their use even when countries are engaged in war.

Congress set a red line when it ratified that treaty. Congress set a red line when it indicated that -- in a piece of legislation titled the Syria Accountability Act -- that some of the horrendous things that are happening on the ground there need to be answered for.

And so when I said in a press conference that my calculus about what’s happening in Syria would be altered by the use of the chemical weapons, which the overwhelming consensus of humanity says is wrong, that wasn’t something I just kind of made up. I didn’t pluck it out of thin air. There’s a reason for it. That’s point No. 1.

Point No. 2 -- my credibility is not on the line. The international community’s credibility is on the line. And America and Congress’ credibility is on the line because we give lip service to the notion that these international norms are important. ... "

The key points: There were two questions; the first was whether he would attack Syria without congressional approval. The second was about the threat to Obama’s credibility.

Obama did not answer the first question.

His answer to the second question began with justifying why the use of chemical weapons ought to be the trigger for an attack. It was a statement about who decided chemical warfare is so bad that it merits that punishment. "I didn’t pluck it out of thin air," he said.

This statement addresses a very different point compared to the first time he used the phrase "red line." It describes why chemical weapon use is a red line. A year earlier, he described in vague terms the consequences of crossing the red line.

The rest of his answer attempted to move the focus away from his political problems and recast it as a moral dilemma every nation faces at this moment.

Obama emphasizes international community

Obama’s answer in Stockholm framed an attack on Syria as a mission of the international community. While this is the first time this argument has stirred controversy, the president has been using it for many months.

A reporter asked: "You said that the red line was not just about chemical weapons being used but being spread, and it was a game-changer -- it seemed cut and dry. And now your administration seems to be suggesting that line is not clear. Do you risk U.S. credibility if you don't take military action?"

Obama: "...There are a whole host of steps that we've been taking precisely because, even separate from the chemical weapons issue, what’s happening in Syria is a blemish on the international community generally, and we've got to make sure that we're doing everything we can to protect the Syrian people.

In that context, what I've also said is that the use of chemical weapons would be a game-changer not simply for the United States but for the international community. And the reason for that is that we have established international law and international norms that say when you use these kinds of weapons you have the potential of killing massive numbers of people in the most inhumane way possible, and the proliferation risks are so significant that we don't want that genie out of the bottle. So when I said that the use of chemical weapons would be a game-changer, that wasn’t unique to -- that wasn’t a position unique to the United States, and it shouldn’t have been a surprise."

The key points: This is quite similar to Obama’s words in Stockholm. He aligns the United Stateswith the international interest in launching a more muscular response in Syria. "We don’t want that genie out of the bottle," he said. "That wasn’t a position unique to the United States." Obama doesn’t deny having said there was a red line, but he does begin to share the implications if Syria crossed it.

Reframing comments rather than denying them

It was just over a year ago that Obama first used the term "red line." In August 2012, he spoke only about the consequences for American policy alone if the red line were crossed. "That would change my calculus," he said.

By April 2013, Obama had broadened his message. On several occasions, he described what made chemical weapons use a red line and why the international community had a stake in containing it.

This September, he was repeating that theme and, with the probable use of chemical weapons by the Syrian government at hand, he was pressuring Congress and the international community to follow his lead. His policy had moved to attack mode, but he was seeking a broader base of support.